Utility of cystatin C-derived equations for evaluation of residual renal function in peritoneal dialysis patients.

BACKGROUND: Residual renal function (RRF) plays a key role in the follow-up of the patients undergoing chronic ambulatory peritoneal dialysis (CAPD). Available methods for measurement of RRF are cumbersome and rarely used, and alternatively, cystatin C-derived equations have been proposed. METHODS: Seventy-six adult CAPD patients were recruited. RRF was measured using the 24-hour urea-creatinine clearance method. Serum concentrations of cystatin C were determined. Glomerular filtration rate (GFR) was estimated using the two published equations of Hoek and colleagues, and Yang and colleagues. GFR was also estimated from serum creatinine using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula. RESULTS: Patients (age range 18-86 years) were on CAPD for a median of 24 months. Average serum concentrations of cystatin C was 5 ± 1.2 mg/L. Average RRF was 0.7 ± 1.6 mL/min/1.73 m(2). All three methods significantly overestimated the measured RRF values (Hoek: 4 ± 1.4; Yang: 4.5 ± 1.5; 7.4 ± 4 mL/min/1.73 m(2)). Based on Bland-Altman plots, all three methods yielded poor agreement with RRF (p < 0.001 for all tests), with Hoek's equation providing the narrowest limits of agreement [mean difference (limits of agreement): 3.4 (2.9-3.9)] and CKD-EPI the widest [6.7 (5.9-7.5)]. Although the Hoek's method outperformed CKD-EPI, the within 30 and 50% accuracy rates were unsatisfactory (10.5 and19.7 %, respectively). CONCLUSIONS: Cystatin C-derived equations outperform the CKD-EPI formula in approximating the RRF values. Yet, these methods still significantly overestimate the measured RRF and their routine application in clinical practice is not advised.

Contribution of stone size to chronic kidney disease in kidney stone formers.

OBJECTIVES: To determine whether stone burden correlates with the degree of chronic kidney disease in kidney stone formers. METHODS: A total of 97 extracorporeal shockwave lithotripsy candidates aged 18 years and older were included. Size, number and location of the kidney stones, along with cumulative stone size, defined as the sum of diameters of all stones) were determined. Estimated glomerular filtration rate was determined using the Chronic Kidney Disease Epidemiology Collaboration cystatin C/creatinine equation, and chronic kidney disease was defined as estimated glomerular filtration rate <60 mL/min/1.73 m(2). RESULTS: In individuals with cumulative stone size <20 mm, estimated glomerular filtration rate significantly decreased when moving from the first (estimated glomerular filtration rate 75.5 ± 17.8 mL/min/1.73 m(2)) to the fourth (estimated glomerular filtration rate 56.4 ± 20.44 mL/min/1.73 m(2) ) quartile (P = 0.004). When patients with a cumulative stone size ≥ 20 mm were included, the observed association was rendered non-significant. In individuals with a cumulative stone size < 20 mm, each 1-mm increase in cumulative stone size was associated with a 20% increased risk of having chronic kidney disease. The relationship persisted even after adjustment for age, sex, body mass index, C-reactive protein, fasting plasma glucose, thyroid stimulating hormone, presence of microalbuminuria, history of renal calculi, history of extracorporeal shockwave lithotripsy, number and location of the stones (odds ratio 1.24, 95% confidence interval 1.02-1.52). The same was not observed for individuals with a cumulative stone size ≥ 20 mm. CONCLUSIONS: In kidney stone formers with a cumulative stone size up to 20 mm, estimated glomerular filtration rate linearly declines with increasing cumulative stone size. Additionally, cumulative stone size is an independent predictor of chronic kidney disease in this group of patients.

Comparison of efficacy of the phosphate binders nicotinic acid and sevelamer hydrochloride in hemodialysis patients.

Hyperphosphatemia is a significant risk factor for the development of ectopic calcification and coronary artery diseases in patients on hemodialysis (HD), and must be controlled with the use of phosphate binders. Studies comparing the effects of sevelamer and nicotinic acid, both similar non-calcium and non-aluminum phosphate binders, are not available. In this study, 40 patients on HD with a serum phosphorus level of more than 6 mg/dL were enrolled. After a two week washout period without phosphate binders, the patients were randomly divided into two equal groups (n = 20) and were started on nicotinic acid or sevelamer for a period of four weeks. The dose of nicotinic acid used was 500 mg and that of sevelamer was 1600 mg daily. Blood samples were drawn for the measurement of the total calcium (Ca), phosphorus (P), alkaline phosphatase (ALP), triglyceride (TG), total cholesterol (Chol), high-density lipoprotein (HDL), low-density lipoprotein (LDL), uric acid and parathyroid hormone (PTH). Patients receiving sevelamer showed a significant reduction in serum P level (2.2 ± 0.69 mg/dL; P <0.0001) in comparison with the nicotinic acid group (1.7 ± 1.06 mg/dL; P = 0.004). Reduction in the Ca-P product was significantly different in the two groups; in the sevelamer group, it was 21 ± 7; (P <0.0001) while in the nicotinic acid group, it was 16 ± 11 (P = 0.007). Also, patients on sevelamer showed greater reduction in the mean TG level (38.9 ± 92 mg/dL; P = 0.005). No significant changes were observed in the mean serum Ca, total Chol, HDL, LDL, ALP and iPTH levels in the two study groups. Our short-term study suggests that although nicotinic acid reduced hyperphosphatemia, sevelamer showed higher efficacy in controlling hyperphosphatemia as well as the Ca-P product.

Oxidative stress status in renal transplant recipients.

OBJECTIVES: Despite the demonstration of oxidative stress in patients with end-stage renal disease, the oxidative status during and after a renal transplant are not completely understood. Hepatocyte growth factor is reported to act as an endogenous factor against oxidative stress. The aim of this study was to evaluate the pattern of changes in plasma oxidative status and hepatocyte growth factor levels in living-donor renal transplant recipients during the early phase after transplant. MATERIALS AND METHODS: Nineteen patients who underwent a renal transplant were included. All were on cyclosporine-based immunosuppression. Plasma levels of malondialdehyde, ferric reducing activity, hepatocyte growth factor, vitamin E, erythrocyte glutathione, and superoxide dismutase activities were determined before, and on the second, seventh, and 12th days after the transplant. RESULTS: High malondialdehyde concentration and low superoxide dismutase activity were seen before and 48 hours after transplant compared with healthy subjects. Significant reductions in plasma ferric reducing activity, malondialdehyde, and hepatocyte growth factor were seen on the seventh and twelfth days after transplant, compared with the before-transplant data. Direct correlations were found between hepatocyte growth factor levels and ferric reducing activity of plasma as well as hepatocyte growth factor and creatinine or uric acid. CONCLUSIONS: Renal transplant recipients display persistent oxidative stress during the early phase of transplant. The pattern of oxidative changes should be considered for appropriate time, dosage, type, and the duration of antioxidant therapy in these patients.

Relation of magnesium level to cyclosporine and metabolic complications in renal transplant recipients.

Cyclosporine is the main immunosuppressive drug used for renal transplant reci-pients in order to prevent transplant rejection. Although the drug has increased the survival of patients and grafted organ, it has some side effects independent of its effect on the immune system. This study was done to evaluate the effect of cyclosporine on serum Mg level and its metabolic side effects in renal allograft patients. 157 (62 female and 95 male) renal transplant recipients treated with cyclosporine to prevent transplant rejection were included in the study. Clinical and biochemical data along with cyclosporine levels was documented. Mean serum Mg level was 196 +/- 0.31 mg/dL and mean serum cyclosporine level was 371 +/- 192 microg/dL. Hypomagnesemia was detected in 16 (10.2%) with a negative significant correlation with cyclosporine levels, serum creatinine, plasma LDL, fasting blood sugar and uric acid. In conclusion according to the results of this study there is a significant correlation between cyclosporine and hypomagnesemia. Therefore, routine measurement of serum Mg and its treatment seems necessary to prevent its complications.

Diagnostic and therapeutic value of short-term corticosteroid therapy in exacerbation of mustard gas-induced chronic bronchitis.

Chronic bronchitis is the most frequent late respiratory disease among Iranians exposed to mustard gas during the Iraq-Iran war. The aim of this study was to investigate efficacy of oral and intravenous corticosteroid therapy in improving lung function in mustard gas induced chronic bronchitis patients. 65 mustard gas-exposed chronic bronchitis patients, who were not responsive to standard treatments in exacerbation occasions, were randomly divided into two groups: an intravenous group (39 patients) receiving 500 mg intravenous methylprednisolone daily, and an oral group (26 patients) receiving 1 mg/kg oral prednisolone daily. Corticosteroid was tapered over the study period in both groups. Spirometery was performed on admission and on day 8 of therapy for assessment of effectiveness of therapy. There was significant improvement in spirometery indexes of both groups in approximately half of the patients over the study period. Furthermore, there was no difference between the pulse corticosteroid versus oral corticosteroid therapy in these patients. Since short-term corticosteroid therapy has a significant effect on lung function of almost fifty percent of patients with mustard gas-induced chronic bronchitis in exacerbation occasions, we suggest a short-term bolus steroid treatment to triage the patients into responders and non-responders for subsequent treatment.